The distribution of chitin synthetase on the yeast plasma membrane will be further studied by electron microscopy and autoradiography. Purification of the solubilized synthetase will be continued with an electrophoretically homogeneous preparation as a goal. Samples of chitin made by yeast in vivo or synthesized in vitro using plasma membranes or solubilized enzyme will be compared, to ascertain how much spatial organization, if any, of the enzyme molecules is necessary to obtain a product identical to the "in vivo" polysaccharide. Mutants defective in chitin synthesis will be studied genetically and biochemically, to ascertain the nature of their defect. The topology of chitin distribution in the yeast cell wall will be examined by electron microscopy, using ferritin-chitinase conjugates. The factors responsible for the protection and activation of a beta-1,3-glucan synthetase will be subjected to further studies. BIBLIOGRAPHIC REFERENCE: Cabib, E.: The yeast primary septum: a journey into three-dimensional biochemistry. Trends in Biochem. Sci. 1: 275-277, 1976.